Biodegradable Self‐Folding Polymer Films with Controlled Thermo‐Triggered Folding

Self‐folding films are a unique kind of thin film. They are able to deform in response to a change in environmental conditions or internal stress and form complex 3D structures. They are very promising candidates for the design of bioscaffolds, which resemble different kinds of biological tissues. In this paper, a very simple and cheap approach for the fabrication of fully biodegradable and biocompatible self‐rolled tubes is reported. The tubes' folding can be triggered by temperature. A bilayer approach is used, where one component is active and another one is passive. The passive one can be any biocompatible, biodegradable, hydrophobic polymer. Gelatin is used as an active component: it allows the design of (i) self‐folding polymer films, which fold at room temperature (22 °C) and irreversibly unfold at 37 °C, and (ii) films, which are unfolded at room temperature (22 °C), but irreversibly fold at 37 °C. The possibilities of encapsulation of neural stem cells are also demonstrated using self‐folded tubes.     

Electroaddressing of Cell Populations by Co‐Deposition with Calcium Alginate Hydrogels

Electroaddressing of biological components at specific device addresses is attractive because it enlists the capabilities of electronics to provide spatiotemporally controlled electrical signals. Here, the electrodeposition of calcium alginate hydrogels at specific electrode addresses is reported. The method employs the low pH generated at the anode to locally solubilize calcium ions from insoluble calcium carbonate. The solubilized Ca²⁺ can then bind alginate to induce this polysaccharide to undergo a localized sol‐gel transition. Calcium alginate gel formation is shown to be spatially controlled in the normal and lateral dimensions. The deposition method is sufficiently benign that it can be used to entrap the bacteria E. coli. The entrapped cells are able to grow and respond to chemical inducers in their environment. Also, the entrapped cells can be liberated from the gel network by adding sodium citrate that can compete with alginate for Ca²⁺ binding. The capabilities of calcium alginate electrodeposition is illustrated by entrapping reporter cells that can recognize the quorum sensing autoinducer 2 (AI‐2) signaling molecule. These reporter cells were observed to recognize and respond to AI‐2 generated from an external bacterial population. Thus, calcium alginate electrodeposition provides a programmable method for the spatiotemporally controllable assembly of cell populations for cell‐based biosensing and for studying cell‐cell signaling.     

Novel Biocompatible Polysaccharide‐Based Self‐Healing Hydrogel

A novel biocompatible polysaccharide‐based self‐healing hydrogel, CEC‐l‐OSA‐l‐ADH hydrogel (“l” means “linked‐by”), is developed by exploiting the dynamic reaction of N‐carboxyethyl chitosan (CEC) and adipic acid dihydrazide (ADH) with oxidized sodium alginate (OSA). The self‐healing ability, as demonstrated by rheological recovery, macroscopic observation, and beam‐shaped strain compression measurement, is attributed to the coexistence of dynamic imine and acylhydrazone bonds in the hydrogel networks. The CEC‐l‐OSA‐l‐ADH hydrogel shows excellent self‐healing ability under physiological conditions with a high healing efficiency (up to 95%) without need for any external stimuli. In addition, the CEC‐l‐OSA‐l‐ADH hydrogel exhibits good cytocompatibility and cell release as demonstrated by three‐dimensional cell encapsulation. With these superior properties, the developed hydrogel holds great potential for applications in various biomedical fields, e.g., as cell or drug delivery carriers.     

三维金属MEMS器件电化学制造技术

EFAB技术是微加工领域一项重大的突破,开辟了MEMS金属器件加工的新天地,与其他微加工技术相比,EFAB技术的主要优点是:可实现MEMS中复杂三维金属微结构器件快速、自动化、批量制造。基于快速原型思想,EFAB利用实时掩模技术将金属材料层层叠加起来,可以加工任意形状的金属三维微结构。介绍了EFAB技术原理,并对其加工设备、分层技术、实时掩模、过程监控等关键技术进行了剖析,最后给出了应用实例。     

微流体光纤芯片的研究进展

微流体光纤芯片是一种把光纤植入到芯片中以方便检测的新型生物芯片,它具有体积小、试剂消耗少、处理速度快、灵敏度高、可实现高度集成等优点,成为微全分析系统(μ—TAS)研究的热点．结合目前光纤芯片的发展状况,综述了两种类型光纤芯片的制作方法,介绍了每种芯片的检测原理,结构及其分类,分析了每种芯片优点与不足,并探讨了其发展趋势．     

光子晶体光纤拉制参数对包层气孔结构的影响

分析了光子晶体光纤(PCF)拉丝工艺参数对光纤毛细管及最终结构的影响,结果表明,通过调节温度、送料速度和拉制速度等参数可以在一定程度上调整最终的气孔结构,但难以拉制出结构完善的PCF.为此提出了惰性气体施压法,实验表明,通过调节施压量的同时结合上述参数的调节,可有效控制光纤的结构参数,拉制出横纵向均匀性良好的PCF.